Rainbow dunes on Mars

A piece of Mars: The dark dune here seems to have a subtle rainbow color across it. Is it a real rainbow? Well, no. Part of it is that I’ve stretched the image to enhance color, so the dark dune should really be more gray than blue. But part of it is real — creamy orange dust has settled in a strip on the left side of the dune, making its contrast with the rest of the dune look like a rainbow. (HiRISE ESP_025001_2255, NASA/JPL/University of Arizona)